Numerical optimization of passive chaotic micromixers

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Due to the lack of turbulence in micromixers diffusion is the main process contributing to microfluidic mixing. Especially mixing of uids with low diffusivity is a difficult task. The recently discovered mechanism of "chaotic-advection" enhances the diffusion process by stretching and folding the fluid interfaces in order to provide a larger interface. Certain passive micromixers like the staggered herringbone mixer (SHM) apply this concept and succeed in enhancing the mixing process considerably. The optimization of such micromixers is a time consuming and often expensive process. We demonstrate that the application of the lattice Boltzmann (LB) method to study advection and diffusion processes can be an efficient tool to optimize micromixers. By combining finite time Lyapunov exponents to study chaotic advection and Danckwert's intensity of segregation to study the diffusion, we demonstrate how optimal geometrical parameters for the SHM can be found and how diffusion is improved by the complex ow pattern inside the mixer. The current article provides a review of our results published in [1] together with additional studies on modelling diffusive mixing with the LB method.This work was financed within the DFG priority program "nano- and microfluidics", the DFG collaborative research center 716, and by the NWO/STW VIDI grant of J. Harting

Regeneration of plants from somatic embryos of Verticillium dahliae-resistant wild olive genotypes

Regeneration capacity, via somatic embryogenesis, of several wild olive genotypes differing in their response to Verticillium wilt (resistant genotypes Stop Vert, Out Vert, Ac4 and Ac 18 and the susceptible Ac 15) has been evaluated. To induce somatic embryogenesis, methodologies previously used in cultivated (high ratio cytokinin/auxin) or wild olive (low ratio cytokinin/auxin) were used. Obtained results revealed the importance of genotype, explant type, mineral formulation and hormonal balance in the induction process, ca. use of apical buds obtained from micropropagated shoots following the methodology of Mazri et al. (2013) in cultivated olive (4 days in liquid medium MS ½, 30 µM TDZ – 0.54 µM ANA, 8 weeks in basal medium MS ½, followed by subculturing in ECO basal medium supplemented with 0.5 µM 2iP, 0.44 µM BA and 0.25 µM IBA) was adequate to obtain somatic embryos in 2 genotypes, Stop Vert and Ac18, but no embryogenic response was observed in the other three. An analysis of genetic stability on Stop Vert, using SSR and RAPDs markers, was carried out in embryogenic callus, plants regenerated form this callus and micropropagated shoots in comparison with the mother plant. Polymorphism was only observed in the banding pattern generated by RAPDs in one of the 10 callus samples evaluated, resulting in a variation rate of 0.07%. This is the first time in which plants have been regenerated via somatic embryogenesis in wild olive.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Research project: Junta de Andalucía P11-AGR799

Duration and cost variability of construction activities: an empirical study

The unique nature of construction projects can mean that construction activities often suffer from duration and cost variability. Because this variability is unplanned, it can present a problem when attempting to complete a project on time and on budget. Various factors causing this variability have been identified in the literature, but they predominantly refer to the nature and/or context of the whole project rather than specific activities. In this paper, the order of magnitude of and correlation between activity duration and cost variability is analyzed in 101 construction projects with over 5,000 activities. To do this, the first four moments (mean, standard deviation, skewness, and kurtosis) of actual versus planned duration and cost (log) ratios are analyzed by project, phase of execution, and activity type. Results suggest that, contrary to common wisdom, construction activities do not end late on average. Instead, the large variability in the activity duration is the major factor causing significant project delays and cost overruns. The values of average activity duration and cost variability gathered in this study will also serve as a reference for construction managers to improve future construction planning and project simulation studies with more realistic data

Transverse Structure of Wind-Driven Flow at the Entrance to an Estuary: Nansemond River

Observations of current velocity profiles were combined with an analytical solution to study the transverse partition of the wind-driven flow in an estuary, the Nansemond River, which is a tributary of the James River in the Chesapeake Bay. Observations spanned two periods of nearly 3 months in autumn-winter of 2003-2004 and spring-summer 2004. The wind-driven circulation consisted of downwind flow over the shoal and upwind flow in the channel at the entrance to the estuary. This pattern developed mainly with landward winds and provided observational evidence that sustains analytical and numerical model results. The transverse structure of the flow showed synoptic temporal variability (3-7 days), which corresponded to the variability of winds and sea level. Synoptic variability seemed to be more influential in autumn-winter than in spring-summer. However, variability of 1-2 days was persistent in both periods of observation. Also, the transverse structure of the wind-driven flows was linked to a counterclockwise recirculation pattern previously observed with survey data. Part of the flow going into the tributary over the shoal might recirculate and form or enhance the outflow in the channel. As suggested by the temporal scale of the wind, the recirculation might weaken or even reverse direction every 3-7 days at the entrance to the estuary. Further detailed studies are needed to better define the extent of this recirculation

Computational modeling of the mechanical modulation of the growth plate by sustained loading

This paper presents a computational model that describes the growth of the bone as a function of the proliferation and hypertrophy of chondrocytes in the growth plate. We have included the effects of the mechanical loads on the sizes of the proliferative and hypertrophic areas, the number of proliferative chondrocytes and the final size of the hypertrophic chondrocytes. The validation of the model was performed with experimental data published on other investigations about proximal tibia of rats, subjected to sustained axial stresses of 0.1 MPa, 0.0 MPa, -0.1 MPa and −0.2 MPa. Growth was simulated during 23 days, obtaining numerical errors between 2.77% and 3.73% with respect to experimental growth rates. The results obtained show that the model adequately simulates the behavior of the growth plate and the effect of mechanical loads over its cellular activity

Licencias ambientales

This article is intended to provide an information tool for obtaining an environmental license, which is based on Decree 2041 of 2014 on environmental licenses, which provides the instructions, entities, and information necessary to carry out the procedures of the licenses. Likewise, the information provided by the environmental authority ANLA (National Authority of Environmental Licenses) is used, since it is fundamental for the drafting of this article. This document is informative and does not pretend to give legal advice, therefore, the people who make use of it will not have any claim for expenses or commitments acquired with the information provided.En este artículo se pretende brindar una herramienta informativa para la obtención de una licencia ambiental, la cual se basa en el decreto 2041 de 2014 sobre licencias ambientales, el cual brinda las instrucciones, entidades e información necesaria para realizar los trámites de las licencias. Igualmente, se hace uso de la información que brinda la autoridad ambiental ANLA (Autoridad Nacional de Licencias Ambientales), ya que es fundamental para la redacción del presente artículo. Este documento es de carácter informativo y no pretende otorgar asesoría legal, por lo cual, las personas que hagan uso de este no tendrán reclamo por gastos o compromisos que se adquiera con la información que se brinda

Quantitative analysis of numerical estimates for the permeability of porous media from lattice-Boltzmann simulations

During the last decade, lattice-Boltzmann (LB) simulations have been improved to become an efficient tool for determining the permeability of porous media samples. However, well known improvements of the original algorithm are often not implemented. These include for example multirelaxation time schemes or improved boundary conditions, as well as different possibilities to impose a pressure gradient. This paper shows that a significant difference of the calculated permeabilities can be found unless one uses a carefully selected setup. We present a detailed discussion of possible simulation setups and quantitative studies of the influence of simulation parameters. We illustrate our results by applying the algorithm to a Fontainebleau sandstone and by comparing our benchmark studies to other numerical permeability measurements in the literature.Comment: 14 pages, 11 figure

El ars inveniendi de Tschirnhaus: un híbrido metodológico y un sustituto del lenguaje universal

La Medicina Mentis de Tschirnhaus, escrita al finalizar el siglo XVII, es una obra poco conocida en la actualidad aunque alcanzó cierta importancia entre los racionalistas alemanes del siglo XVIII, principalmente Wolff y Lambert. Además, aunque puede no poseer novedades significativas, resulta de gran interés por ser una obra ecléctica que concentra distintas ideas epistemológicas y metodológicas y, en ese sentido, es un claro reflejo de las corrientes de pensamiento que se enfrentaron durante el siglo XVII .En la presente ponencia intentamos una revisión de la invención a fin de reubicarlo en el lugar que le corresponde de acuerdo a su verdadera naturaleza. En primer lugar, mostraremos el desfasaje que existe entre el realce de su orientación heurística y del análisis, en las primeras páginas de la obra, frente a la gran importancia que se concede a la síntesis en otras partes menos visibles. Aquí, además, sale a la luz una diferencia muy importante con Descartes respecto del valor que se concede al análisis y la síntesis. Luego, mediante un recorrido por los aspectos metodológicos de la obra, mostraremos que este desfasaje también se nota en la estructura misma del método. Finalmente haremos notar de pasada algunas posibles correspondencias entre el método propuesto por Tschirnhaus y la idea de lenguaje universal que rondaba las mentes del siglo XVII. (Párrafo extraído del texto a modo de resumen)Departamento de Filosofí

Mathematical and physical techniques of modeling and simulation of pattern recognition in the stock market

The following article presents the analysis through mathematical and physical techniques of large databases, which are very common today, due to the large number of variables (especially in the information and physics industry) and the amount of information that results from a process, therefore an analysis is necessary that allows the Decision in a responsible manner, looking for scientific criteria that support said decisions, in our case a database of the forex system will be taken. Initially, a study and calculation of different measurements between the samples and their characteristics will be carried out to make a good prediction of the data and their behavior using different classification methods inspired by basic sciences. Below is an explanation of the techniques based on the analysis of data components and the correlations that exist between the variables, which is a technique widely used in physical processes to determine the correlations between variables